Paper 1 Alternating Current Answers

Q	Answer	Reason
1	B	AC reverses direction periodically.
2	A	Amplitude is peak value.
3	A	Rms is heating-equivalent dc value.
4	A	For sinusoid.
5	A	Frequency is reciprocal of period.
6	A	Angular frequency relation.
7	A	Positive and negative halves cancel.
8	A	For a pure resistor using rms values.
9	A	Ohmic resistor voltage/current are in phase.
10	A	This gives rms factor.
11	A	From negative peak to positive peak.
12	A	Output has one direction but varies.
13	A	Bridge/full-wave uses both halves.
14	A	Smoothing capacitor charges/discharges to reduce ripple.
15	A	$\omega =100\pi =2\pi f$, so $f=50$ Hz.
16	B	Mains voltages are rms unless stated.
17	A	$I=V/R=2.0$ A.
18	A	$I_0=\sqrt{2}{I}_{rms}=5.66$ A.
19	A	Heating depends on rms current squared.
20	A	Definition of rms.